Objectives: To determine the effect of caries prevalence of varying concentrations of Strontium in communal water supplies with optimum fluoride. To relate caries prevalence with strontium levels in drinking water, whole and surface human enamel and plaque. To assess the ability of enamel with varying concentrations of strontium to resist demineralization and dissolution. Methods: Caries prevalence in 12-14 year old children in selected cities of Wisconsin will be determined by an epidemiologic survey. Chemical analysis of whole and surface enamel, plaque, and communal water supplies for strontium and fluoride will be carried out by in house chemistry. Methods will include atomic absorption spectrophotometry for strontium, ion selective electrode and hydrogen fluoride diffusion for fluoride.